Plastic has taken the place of other materials in a variety of industries. In the packaging industry, plastic has replaced glass to minimize breakage, reduce weight, and reduce energy consumed in manufacturing and transport. In other industries, plastic has replaced metal to minimize corrosion, reduce weight, and provide color-in-bulk products. Recently, an entire industry has arisen called “wood polymer composites” (WPC).
Wood polymer composites are based on the premise that use of biofiber, such as wood fiber and other naturally occurring particulates, as additives to thermoplastic compounds can simulate the appearance of wood while also providing the durability of plastic. Outdoor decorative and structural wood building materials, such as decking, railings, windows, etc. are being made from WPC materials.
The ability of the WPC material to simulate the appearance of the natural wood, including its surface texture and wood grain coloration is key to value of the WPC to successfully replace the natural wood itself. Moreover, use of common wood fiber, such as pine, to simulate the appearance of exotic wood is environmentally friendly.
The art has attempted, without success, to provide durable coloration of WPC materials. Inevitably, the coloration is added as a part of the thermoplastic compounding process, but association of the pigment or dye of such coloration with the wood fiber is circumstantial at best.
U.S. Patent Publication 2004/0076847 (Saunders Jr. et al.), now abandoned during examination, taught the attempt to color the wood fiber with commercially available pigment dispersions or dye solutions which also contained adjuvants such as thickeners, surfactants, etc. U.S. Pat. No. 6,207,228 (Hundt et al.) taught the use of impregnated waste wood to be bound on the one hand to make plasticized wood products and coloration of wood on the other hand with color impregnating agents of pigment or dye plus fillers or extenders.